1. Field of the Invention
The present invention generally relates to communication systems and, more particularly, to a synchronization loss resilient digital communication system using Forward Erasure Correction (FXC).
2. Background of the Invention
Wireless digital communications systems are subject to multi-path and fades, which can lead to loss of synchronization. The data transmitted during periods of lost synchronization are normally lost to the receiver. Thus, the problem to be solved is how to design a wireless digital communication system that is resilient to synchronization loss due to multi-path and fading, with as low an overhead rate as possible.
The effects of multi-path and fading effects on Wireless digital communication links are well understood and their probability characteristics have been documented. For example, in Advanced Television Systems Committee (ATSC) 8 Vestigial Side Band (8VSB) transmission systems for High Definition Television (HDTV) broadcast in the United States, the probability distribution of fade duration has been studied. Reception of the 8VSB system on a mobile device further increases the probability of synchronization loss. Even after synchronization is reacquired, useful data cannot be recovered in an ATSC 8VSB system until trellis decoding is re-trained, and an interleaver begins a new block.
The ATSC 8VSB system includes several types of channel coding to protect against noisy transmission, including trellis coding, interleaving, and Reed Solomon (RS) Forward Error Correction (FEC). But when synchronization loss occurs, the channel coding methods used do not assist in recovering the data.
Repeatedly transmitting data can improve system resiliency synchronization loss, but at the cost of high overhead. Allocating more of the available bandwidth to repeated transmission of data reduces the amount of original data that can be transmitted, which means fewer programs, or lower quality of transmitted programs.
It has also been proposed that instead of repeatedly transmitting the original data, the overhead rate could be reduced by redundantly transmitting a lower bit-rate version of the original data. When the original data is lost due to synchronization loss, the reduced resolution version is used by the receiver. This allows graceful degradation, i.e., a lower quality version of the original data is available rather than the original data. However, if the original higher resolution data is required, the reduced resolution version may prove unsatisfactory.
Accordingly, it would be desirable and highly advantageous to have a synchronization loss resilient digital communications system that overcomes the above stated problems of the prior art.